Optical centers, interaction with effect

The fundamentals of SSS are based on the theory of impurity centers in a crystal. The optical spectrum of an organic molecule embedded in a matrix is defined by electron-vibrational interaction with intramolecular vibrations (vibronic coupling) and interaction with vibrations of the solvent (electron-phonon coupling). Each vibronic band consists of a narrow zero-phonon line (ZPL) and a relatively broad phonon wing (PW). ZPL corresponds to a molecular transition with no change in the number of phonons in the matrix (an optical analogy of the resonance -line in the Mossbauer effect). PW is determined by a transition which is accompanied by creation or annihilation of matrix phonons. The relative distribution of the integrated intensity of a band between ZPL and PW is characterized by the Debye-Waller factor ... 

Tartrate-resistance (see below) was one of the first observations concerning the purple acid phosphatases with binuclear iron centers Consistent with this is the absence of any effect of tartrate on either the optical or EPR spectrum of pink uteroferrin, indicating that this anion interacts weakly, if at all, with the active binuclear iron center ... 

Electron hyperfine interactions created by optical illumination can have marked effects upon semiconductor relaxation. The mCd and n3Cd peaks in CdS at 4.2 K showed a marked reduction from 3 x 103 min to 30 min during illumination with white light, and remained at 4 x 102 min after the light was turned off [241]. Paramagnetic relaxation centers created by the light were responsible. 

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